Distillation of oil-bearing minerals



Dec. 1954 L. A. NlCOLAl DISTILLATION OF OIL-BEARING MINERALS Filed Nov. 30, 1949 PRODUC 7' VA PORS RAW .SHALE HOPPER M M T s COARSE .SHA LE DISCARD Ana B yQQ/ZMW W DISTILLATION or on-nnannso MINERALS Lloyd A. Nicolai, Baton Rouge, 1a., assignor to Standard Oil Development Company, a corporation of Delaware Application November 30, 1949, Serial No. 130,140

9 Claims. (Cl. 202l2) The present invention relates to the distillation of oil-bearing minerals of the type of oil shale, oil sands, tar sands or the like, which tend to disintegrate upon distillation. More particularly, the present invention relates to an improved process of distilling oil shale wherein the heat required for the distillation is supplied by carrying out the distillation in indirect heat exchange with a heat transfer fluid highly heated by an indirect heat exchange with burning retorted shale and wherein the solids in the distillation and burning zones are maintained in the form of relatively dense turbulent masses fluidized by upwardly flowing gases.

it is Known that certain types of naturally occurring oil-bearing minerals, such as oil shales, contain materials which .may be converted by a pyrolytic treatment into hydrocarbon oils in commercially feasible yields. Prior to the present invention, others proposed carrying out the pyrolytic treatment of the shale in the form of a powder or larger aggregate of up to A1 in. diameter, in a highly turbulent state fluidized by an upwardly flowing gas, in a distillation zone, while supplying the heat necessary for the reaction by combustion, that is either by burning a portion of the combustibles in the distillation zone in a system of the single vessel type, or by burning the spent shale in a separate combustion zone and returning the burnt substantially uncooled shale to the distillation zone for heat supply, in a system of the two-vessel type.

The former method, while simple in design, involves the disadvantages of product losses by combustion and product dilution with flue gases. The latter method avoids these drawbacks, but it is conducive to extreme shale disintegration and excessive fines entrainment from the distillation zone. In addition, oil yields are seriously affected by the adsorption in the retort of retorted oil on the circulated burnt shale followed by combustion of the adsorbed oil in the burner.

The present invention overcomes these ditficulties and affords various additional advantages as will appear from the description below wherein reference will be made to the accompanying drawing.

In accordance with the present invention, the heat generated in the combustion zone of a two-vessel system of the type referred to above is transferred to the distillation zone by means of an extraneous heat-carrying medium which boils at a temperature not exceeding that of the combustion zone and condenses at the temperatures prevailing in the distillation zone at moderate pressures of approximately atmospheric up to about 10 atmospheres gauge. It has been found that elemental sulfur complies with these requirements for all practical purposes.

For example, in a combustion zone operating at about 1200-l400 F., sulfur will boil readily at pressures'of about 5 atmospheres gauge. At the same pressure, sulfur will condense at temperatures in the neighborhood of about 950 P. which are optimum for the fluid-type distillation of most oil shales. in its more specific aspects, therefore, the present invention provides for a flow of retorted shale from a fluidized distillation zone to a fluidized combustion zone wherein the retorted shale is burned to generate heat, for the circulation of sulfur vapors generated in heat transfer means confined within the fluidized mass of the combustion zone to heat transfer means confined Within the fluidized mass of the distillation zone and for a recirculation of condensed liquid sulfur from the last named heat transfer means to the first named heat transfer means. In accordance with the States Patent 0 "ice preferred embodiment of the invention, the distillation zone is arranged above the combustion zone and the sulfur is permitted to circulate within the heat transfer circuit in a manner generally analogous to the principle of reflux condensation.

The efficiency of a system of this type depends largely on the heat transfer coelficient of the heat exchange surfaces used which should also be highly resistant against heat and corrosion. When such heat and corrosion resistant materials, such as 25-20 chrome-nickel alloyed steel, are used, heat transfer areas of about .01-.025 sq. ft. per lb. per hour of raw shale feed, in the combustion zone, and about .01.03 sq. ft. per lb. per hour of raw shale feed, in the distillation zone, are normally sufficient considering the excellent heat transfer characteristics of dense, turbulent, fluidized solids masses and of boiling and condensing liquids.

Having set forth its objects and general nature, the invention will be best understood from the more detailed description hereinafter read with reference to the accompanying drawing, the single figure of which is a semidiagrammatic illustration of a system suitable to carry out a preferred embodiment of. the invention.

Referring now to the drawing, the system illustrated therein essentially comprises a fluid-type distillation zone or retort 10 and a fluid-type combustion zone or burner 30 located at a lower level than retort 10. The lower portion of retort 10 is connected with the upper portion of burner 30 by a pipe 2t? provided with a metering device such as a slide valve 22. Retort 10 contains a set of heat transfer tubes 15 which may be made of an alloyed steel of the type mentioned above and burner 30 contains a similar set of tubes 35. Tubes 15 are connected with tubes 35 via headers 17 and 37 through a single pipe 25. Tubes 15 may have an area of about .028 sq. ft. per lb. per hour of cold shale feed and tubes 35 may have an area of about .022 sq. ft. per lb. per hour of cold shale feed. Of course, these areas can be greatly reduced if the shale feed is preheated before entering vessel 10. The diameter of pipe 25 should be large enough to permit the free return of liquid from tubes 35. Heat exchange system 15, 25, 35 contains elemental sulfur in a mixed vapor-liquid state. About .04-.06 lbs. of sulfur per lb. per hour of cold shale feed are normally adequate to take care of the heat transfer requirements of the system.

in operation, raw oil shale crushed to a particle size passing 4 mesh is supplied from feed hopper 1 via line 3 .provided with control valve 5 to an upper portion of retort 10. The shale within retort 10 is maintained in the form of a highly turbulent fluidized mass M1 having an upper level L10, by the combined action of rising distillation vapors and a fluidizing and stripping gas such as steam, product tail gas or the like introduced into a lower portion of retort 10. As shown in the drawing, steam is introduced for this purpose through line 27 into pipe 20. This steam serves simultaneously as a stripping medium for retorted shale to remove adhering distillation products. The steam feed rate should be so con trolled that a superficial linear gas velocity of about 0.5-1.5 ft. per second exists in mass M10. Distillation takes place in mass M10 under the influence of the sensible heat and heat of condensation of sulfur vapor condensing in tubes 15 to maintain a distillation temperature of about 900950 F. At these conditions, the relatively coarse fresh shale distills and disintegrates rapidly to assume a readily fluidizable particle size distribution and to form turbulent mass M10 having an apparent density of about 10-30 lbs. per cu. ft.

A mixture of gasiform distillation products and fluidizing gas is withdrawn overhead from level L10 and passed through line 12 to conventional product recovery equipment (not shown) preferably after suitable heat recovery and separation of entrained solids fines, all in a manner known per se in the art of fluid shale retorting. Retorted shale is withdrawn from the bottom of retort 10 through pipe 20 wherein it is stripped with steam as above described. The stripped shale enters the top of burner 30 at a rate controlled by slide valve 22. A combustion-supporting gas, such as air, is supplied through line 39 to the bottom of burner 30 and enters in the drawing.

a perforated grid 41. Sufiicient air is supplied to maintam by combustion of retorted shale a temperature of about 1200-1400 F. in burner 30. About 3-5 normal cu. ft. of air per 1b of cold shale feed is usually adequate for this purpose. The air feed rate is preferably so controlled that a superficial linear gas velocity of about 0.5-1.5 ft. per second exisits within mass M30 which then assumes the form of a turbulent fluidized solids mass having an apparent density of about 10-3O lbs. per cu. ft. Flue gases containing entrained solids fines may be withdrawn overhead from level L30 via line 43, preferably after conventional heat recovery and solids separation. Relative coarse burnt shale accumulating in the bottom of burner 30 may be withdrawn through line 45 as required and discarded, if desired, after a suitable recovery of its sensible heat.

At the conditions specified, the sulfur flowing down pipe 25 in liquid form boils continuously in tubes 35 at a temperature of about 1050 F. and a pressure of about 5 atmospheres gauge. The sulfur vapors so developed rise through pipe 25 to give off their heat of condensation at the same pressure through the walls of tubes 15 at about 1050 F. to a bed having a temperature of about 950 F.

The system illustrated by the drawing may be modified in various respects without deviating from the spirit of the invention. For example, vessels and 30 may be arranged in relative positions different from that shown It is noted, however, that the arrangement of the burner below the retort permits fully automatic and continuous operation without the use of high temperature pumps for the heat transfer medium or special conveying means for the fluidized solids. Other heat transfer media, such as water, mercury, or other metals, are much less desirable than sulfur because the use of these media requires the application of excessive pressures or substantial vacuums to effect boiling and condensation at temperatures suitable for shale distillation.

The above description and exemplary operations have served to illustrate specific embodiments of the invention but are not intended to be limiting in scope.

What is claimed is:

1. The process of distilling subdivided oil-bearing shale and the like which comprises fiuidizing said shale in a first zone and distilling it with heat transfer means in said first zone to remove volatilizable oils therefrom, withdrawing the devolatilized shale by gravity to a second zone below said first zone, fiuidizing said devolatilized shale and burning off combustible material on said devolatilized shale in said second zone to supply heat to a heat transfer means, and continuously refluxing sulfur volatile in the burning zone and condensable in the distilling zone in both directions between said heat transfer means, thereby utilizing the heat of combustion in said burning zone to carry out the distillation.

2. In apparatus for distilling subdivided oil shale to remove volatilizable oil therefrom, the combination of a distillation retort adapted to receive said shale, means for fiuidizing said shale in said retort to obtain effective heat transfer at distillation temperatures, a burning chamber below said retort adapted to burn the combustible residues on spent shale at a higher temperature, means for supplying oxidizing gas to said chamber and for fiuidizing subdivided solids therein, means for feeding spent shale by gravity from said retort to said chamber, a heat transfer means in both said retort and in said chamber and a single conduit connecting said transfer means, there being within said conduit and transfer means a quantity of sulfur sufiicient to serve as a heat transfer fluid vaporizable at the temperature of said burning chamber and at pressures of 1 to 10 atmospheres and condensable at the temperature of said distillation retort to transfer latent heat of evaporation as well as sensible heat from the burning chamber to the retort.

3. The process of claim 1 in which said combustion zone is arranged at a level lower than said distillation zone and said medium is circulated through said circuit in the manner of reflux condensation.

4. The process of claim 1 in which said distillation is carried out in the absence of shale burned in said combustion zone.

5. The process of claim 1 in which said pressures fall within the range of 1-10 atmospheres absolute.

6. The process of claim 1 in which said medium is sulfur, said distillation temperature is about 900-950 F., said higher temperature is about 12001400 F. and said pressure is about 5 atmospheres gauge.

7. A process for recovering oil from oil shale and like carbonaceous minerals which comprises subdividing said minerals into particles of fluidizable size, fiuidizing said particles in one zone with a fiuidizing gas substantially free of combustion gases, applying sufficient heat by indirect heat transfer from a quantity of sulfur in the form of a vapor condensable at the distillation temperature for said mineral to substantially remove the oil from said fluidized particles, transferring the de-oiled particles to a combustion zone, fiuidizing the de-oiled particles in said combustion zone with an oxidizing gas to heat them by burning the carbonaceous residues associated with said particles, absorbing said heat by indirect heat exchange into the condensate aforesaid, and refluxing the vapors and condensate respectively between said zones.

8. Process according to claim 7 wherein the distillation temperature is about 950 F. and the combustion temperature is between about 1200 and 1400 F.

9. Process according to claim 7 wherein the distillation zone is above the combustion zone, a stripping zone is interposed between, and the mineral residue from the distillation passes by gravity through said stripping zone en route to the combustion zone.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,547,167 Downs July 28, 1925 1,589,632 Downs June 22, 1926 1,704,956 Trumble Mar. 12, 1929 1,984,380 Odell Dec. 18, 1934 2,331,433 Simpson et al Oct. 12, 1943 2,412,025 Zimmerman Dec. 3, 1946 2,416,730 Arveson Mar. 4, 1947 2,119,091 Atkinson et al. May 31, 1948 2,445,327 Keith July 20, 1948 2,480,670 Peck Aug. 30, 1949 2,490,993 Borcherding Dec. 13, 1949 2,544,843 Leffer Mar. 13, 1951 2,581,041 Ogorzaly et a1 Jan. 1, 1952 FOREIGN PATENTS Number Country Date 506,544 Germany Sept. 5, 1930 107,907 Australia July 5, 1939 

1. THE PROCESS OF DISTILLING SUBDIVIDED OIL-BEARING SHALE AND THE LIKE WHICH COMPRISES FLUIDIZING SAID SHALE IN A FIRST ZONE AND DISTILLING IT WITH HEAT TRANSFER MEANS IN SAID FIRST ZONE TO REMOVE VOLATILIZABLE OILS THEREFROM, WITHDRAWING THE DEVOLATILIZED SHALE BY GRAVITY TO A SECOND ZONE BELOW SAID FIRST ZONE, FLUIDIZING SADI DEVOLATILIZED SHALE AND BURNING OFF COMBUSTIBLE MATERIAL ON SAID DEVOLATILIZED SHALE IN SAID SECOND ZONE TO SUPPLY HEAT TO A HEAT TRANSFER MEANS, AND CONTINUOUSLY REFLUXING SULFUR VOLATILE IN THE BURNING ZONE AND CONDENSABLE IN THE DISTILLING ZONE IN BOTH DIRECTIONS BETWEEN SAID HEAT TRANSFER MEANS, THEREBY UTILIZING THE HEAT OF COMBUSTION IN SAID BURNING ZONE TO CARRY OUT THE DISTILLATION. 